Photo storage is full when it really isn't?

I can make calls and receive them also text and receive. My browser works but I can not take a photo because the iPhone says that my storage is full, when really by all indications it is not. I have deleted all apps, taken the phone back to the iPhone store and had them look at it, they reset it back to factory settings and I was able to take photos for about two days (less than 25 photos) then the same error occurred... storage full. I have small children and the grand parents are starting to complain about not seeing any videos of the kids. Please help